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  • 1.
    Blumenau, A.T.
    et al.
    Max-Planck-Institut für Eisenforschung GmbH.
    Eberlein, T.A.G.
    School of Physics, University of Exeter.
    Jones, R.
    School of Physics, University of Exeter.
    Öberg, Sven
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mathematical Science.
    Frauenheim, T.
    Theoretische Physik, Universität Paderborn.
    Briddon, P.R.
    Department of Physics, University of Newcastle.
    The effect of charge on kink migration at 90° partial dislocations in SiC2005In: Physica Status Solidi (a) applications and materials science, ISSN 1862-6300, E-ISSN 1862-6319, Vol. 202, no 5, p. 877-882Article in journal (Refereed)
    Abstract [en]

    SiC bipolar devices show a degradation under forward-biased operation which has been linked with a recombination enhanced motion of one of the two glide dislocations having either Si or C core atoms. We have carried out calculations of the core structures and dynamics of partial dislocations in 3C and 2H-SiC using the density functional based codes DFTB and AIMPRO. After in earlier theoretical work we reported on the structure, energetics and electronic activity of both of the Shockley partials, and on the formation and migration barriers of kinks, in this work we present first results on the effect of charge on the disloction kinks. The calculations give insights into the device degradation mechanism.

  • 2.
    Carvalho, Alexandra
    et al.
    Department of Physics, I3N, University of Aveiro, Campus Santiago.
    Santos, Paulo
    Department of Physics, I3N, University of Aveiro, Campus Santiago.
    Coutinho, José
    Department of Physics, I3N, University of Aveiro, Campus Santiago.
    Jones, Robert
    School of Physics, University of Exeter.
    Rayson, Mark
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mathematical Science.
    Briddon, Patrick R.
    Electrical, Electronic and Computer Engineering, University of Newcastle upon Tyne.
    Light induced degradation in B doped Cz-Si solar cells2012In: Physica Status Solidi (a) applications and materials science, ISSN 1862-6300, E-ISSN 1862-6319, Vol. 209, no 10, p. 1894-1897Article in journal (Refereed)
    Abstract [en]

    We analyse the formation energy of interstitial boron (Bi) and the properties of the defect resulting from its association with an oxygen dimer (BiO2i) to evaluate the possibility that it may be the slow-forming centre responsible for the light-induced degradation of B-doped Si solar cells. However, we find that the formation energy of Bi is too high, and therefore its concentration is negligible. Moreover, we find that the lowest energy form of BiO2i is a shallow donor, and the deep donor form is high in energy. Lowest energy structure of the BiO2i defect.

  • 3.
    Carvalho, Alexandra
    et al.
    Department of Physics, I3N, University of Aveiro, Campus Santiago.
    Öberg, Sven
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mathematical Science.
    Barroso, Manuel
    Department of Physics, I3N, University of Aveiro, Campus Santiago.
    Rayson, Mark
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mathematical Science.
    Briddon, Patrick
    Electrical, Electronic and Computer Engineering, University of Newcastle upon Tyne.
    P-doping of Si nanoparticles: the effect of oxidation2012In: Physica Status Solidi (a) applications and materials science, ISSN 1862-6300, E-ISSN 1862-6319, Vol. 209, no 10, p. 1847-1850Article in journal (Refereed)
    Abstract [en]

    The radial dependence of the formation energy of substitutional phosphorus in silicon nanoparticles covered by an amorphous oxide shell is analysed using local density functional theory calculations. It is found that P+ is more stable at the silicon core. This explains the experimental observation of segregation of phosphorus to the Si-rich regions in a material consisting of Si nanocrystals embedded in a SiO2 matrix [Perego et al., Nanotechnology 21, 025602 (2010)]. Formation energy of positively charged substitutional phosphorus in a 1.5 nm diameter Si nanoparticle covered by a ∼2 nm-thick amorphous SiO2 shell, as a function of its distance to the centre.

  • 4.
    Fujita, N.
    et al.
    School of Physics, University of Exeter.
    Blumenau, A.T.
    Max-Planck-Institut für Eisenforschung GmbH.
    Jones, R.
    School of Physics, University of Exeter.
    Öberg, Sven
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mathematical Science.
    Briddon, P.R.
    School of Natural Science, University of Newcastle upon Tyne.
    Core reconstructions of the (100) edge dislocation in single crystal CVD diamond2007In: Physica Status Solidi (a) applications and materials science, ISSN 1862-6300, E-ISSN 1862-6319, Vol. 204, no 7, p. 2211-2215Article in journal (Refereed)
    Abstract [en]

    Dislocations are common defects in both natural as well as in CVD-grown diamond. Recent advances in the growth of high quality single crystal CVD diamond have led to an increased interest in the atomistic and electronic structure of 100 dislocations. These dislocations are observed as mixed-type 45° and pure edge dislocations. Previously we investigated both types and found that the 45° is by far lower in core energy than the proposed structure of the edge type. In this work we focus on the straight 100 dislocation only and present novel core reconstructions. We find a minimum energy structure for the edge-type dislocation which has a similar core energy as the mixed-type dislocation.

  • 5.
    Fujita, N.
    et al.
    School of Physics, University of Exeter.
    Blumenau, A.T.
    Max-Planck-Institut für Eisenforschung GmbH.
    Jones, R.
    School of Physics, University of Exeter.
    Öberg, Sven
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mathematical Science.
    Briddon, P.R.
    School of Natural Science, University of Newcastle upon Tyne.
    Theoretical studies on ‹100› dislocations in single crystal CVD diamond2006In: Physica Status Solidi (a) applications and materials science, ISSN 1862-6300, E-ISSN 1862-6319, Vol. 203, no 12, p. 3070-3075Article in journal (Refereed)
    Abstract [en]

    Dislocations are common defects in both natural as well as in CVD-grown diamond. Recent advances in the growth of high quality single crystal CVD diamond have led to an increased interest in the atomistic and electronic structure of ‹100› dislocations. These dislocations are observed as mixed-type 45° and pure edge dislocations. Hence in this work we present ab initio modelling studies on these two types of dislocations. The 45° dislocation is found to be by far more stable than the pure edge and both dislocations lead to states in the electronic band gap. An alternative structure for the mixed-type dislocation, which is not straight but kinked and consists of short edge and screw segments, was found slightly higher in energy than the straight structure.

  • 6.
    Hounsome, L.S.
    et al.
    School of Physics, University of Exeter, UK.
    Jones, R.
    School of Physics, University of Exeter, UK.
    Martineau, P.M.
    DTC, Maidenhead.
    Shaw, M.J.
    School of Natural Science, University of Newcastle upon Tyne, UK.
    Briddon, P.R.
    School of Natural Science, University of Newcastle upon Tyne, UK.
    Öberg, Sven
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mathematical Science.
    Blumenau, A.T.
    Max-Planck-Institut für Eisenforschung GmbH.
    Fujita, N.
    School of Physics, University of Exeter, UK.
    Optical properties of vacancy related defects in diamond2005In: Physica Status Solidi (a) applications and materials science, ISSN 1862-6300, E-ISSN 1862-6319, Vol. 202, no 11, p. 2182-2187Article in journal (Refereed)
    Abstract [en]

    ‹110› vacancy chains, multi-vacancy clusters and vacancy discs have been modeled using density functional theory within the AIMPRO and DFTB codes. While a connection can be established between the results on vacancy chains and previous EPR experiments, no connection can be made between the point defects and the optical properties of natural type IIa brown diamonds. However, a vacancy disc consisting of a {111} double plane of vacancies is stable and possesses an absorption spectrum similar to that found in brown diamonds.

  • 7.
    Jones, Robert
    et al.
    University of Exeter.
    Hounsome, Luke S.
    University of Exeter.
    Fujita, Naomi
    University of Exeter.
    Öberg, Sven
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mathematical Science.
    Briddon, Patrick R.
    University of Newcastle.
    Electrical and optical properties of multivacancy centres in diamond2007In: Physica Status Solidi (a) applications and materials science, ISSN 1862-6300, E-ISSN 1862-6319, Vol. 204, no 9, p. 3059-3064Article in journal (Refereed)
    Abstract [en]

    Recent experiments have shown that vacancy clusters are common defects in all types of monocrystalline brown diamond. This is believed to be due to an enhanced stability of the bounding (I 11) or (I 10) surfaces, arising from the formation of pi-bonded chains. These chains lead to broad bands of gap states with acceptor and donor levels around E-v + 2 eV. They also are likely to be responsible for the broad absorption continuum extending from the NIR through the visible and into the UV region which is characteristic of brown diamonds. High temperature treatment removes or transforms the clusters in CVD and type IIa diamonds leaving the diamond colourless. In type la brown diamonds, heat treatments up to 2500 degrees C lead to the breakup of the clusters and the formation of specific vacancy-nitrogen defects. We show that ab initio modelling of the interaction of nitrogen with the chains open a gap and leads to a threshold absorption energy in the 1-2 eV range. Finally, the calculations shed light on the identity of the vacancy-nitrogen defects observed.

  • 8.
    Memarian, Nafiseh
    et al.
    Faculty of Physics, Semnan University, P.O. Box: 35195-363, Semnan, Iran.
    Farahi, Ehsan
    Faculty of Physics, Semnan University, P.O. Box: 35195-363, Semnan, Iran.
    Tobeiha, Nafiseh
    Faculty of Physics, Semnan University, P.O. Box: 35195-363, Semnan, Iran.
    You, Sujie
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Concina, Isabella
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Understanding Graphitic Carbon Nitride as Photocatalyst: A Case Study on Thermal Engineering of Physical and Chemical Features2024In: Physica Status Solidi (a) applications and materials science, ISSN 1862-6300, E-ISSN 1862-6319, Vol. 221, no 7, article id 2300844Article in journal (Refereed)
    Abstract [en]

    Rationalizing material features according to the adopted synthetic strategy, aiming then to tune them on demand, is among the most relevant purposes of investigation in materials science. Herein, the systematic analysis of the dependence of graphitic carbon nitride (g-C3N4) physical characteristics on the decomposition temperature of urea, rationalizing the impact of synthetic temperature on several characteristics of the materials (degree of N–H condensation, carbon vs nitrogen content, structural parameters, photoluminescence lifetime, surface area, pores volume), is discussed. g-C3N4 nanostructures are fabricated by thermal decomposition of urea at different temperatures under ambient atmosphere, obtaining an almost ideal stoichiometry (C/N = 0.72) when setting the temperature at 600 °C. The samples show structural, textural, compositional, and optical differences directly depending on the fabrication temperature: specific surface area, pore volume and size, intralayer distance, and speed of radiative recombination of photogenerated charges are proportionally enhanced by increasing the synthesis temperature. The role played by all the physicochemical features of the prepared samples in promoting the catalytic degradation of Rhodamine B is investigated, highlighting their synergistic role in enhancing the catalytic efficiency. Significant differences in the dye degradation are recorded when using either UV or solar simulated light, demonstrating that Rhodamine B photosensitization rules the process.

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  • 9.
    Pinto, H.
    et al.
    College of Engineering, Mathematics and Physical Sciences, University of Exeter, Stocker Road, Exeter, EX4 4QL, UK.
    Jones, R.
    College of Engineering, Mathematics and Physical Sciences, University of Exeter, Stocker Road, Exeter, EX4 4QL, UK.
    Palmer, D. W.
    College of Engineering, Mathematics and Physical Sciences, University of Exeter, Stocker Road, Exeter, EX4 4QL, UK.
    Goss, J. P.
    School of Electrical, Electronic and Computer Engineering, Newcastle University, Newcastle upon Tyne, NE1 7RU, UK.
    Briddon, P. R.
    School of Electrical, Electronic and Computer Engineering, Newcastle University, Newcastle upon Tyne, NE1 7RU, UK.
    Öberg, Sven
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mathematical Science.
    Theory of the surface effects on the luminescence of the NV(-) defect in nanodiamond2011In: Physica Status Solidi (a) applications and materials science, ISSN 1862-6300, E-ISSN 1862-6319, Vol. 208, no 9, p. 2045-2050Article in journal (Refereed)
    Abstract [en]

    A vacancy with one of the carbon neighbours replaced by a nitrogen atom in diamond (the NV centre) is a defect of particular interest due to its many potential applications. In the negatively charged state, the defect is paramagnetic with spin 1 and under optical excitation it exhibits an intense luminescence with a zero-phonon line at 1.945eV. This fluorescence is found in nanodiamonds even as small as 5nm and an important question is the effect of the surface of the nanodiamond on the optical emission of NV-.

    Density functional calculations are used in this work to investigate the effect of the bare (001) and (001)-OH diamond surfaces on the electronic structure of NV-. We show that the (001)-OH diamond surface has the minimum interaction with the defect and is the ideal terminating surface of nanodiamonds, while the bare (001) diamond surface has a strong effect on broadening the emission.

  • 10.
    Pinto, H.
    et al.
    Hungarian Academy of Sciences, Wigner Research Centre for Physics, Institute for Solid State Physics and Optics.
    Jones, R.
    College of Engineering, Mathematics and Physical Sciences, University of Exeter.
    Palmer, D.W.
    College of Engineering, Mathematics and Physical Sciences, University of Exeter.
    Goss, J.P.
    School of Electrical, Electronic and Computer Engineering, University of Newcastle upon Tyne.
    Briddon, P.R.
    School of Electrical, Electronic and Computer Engineering, University of Newcastle upon Tyne.
    Öberg, Sven
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mathematical Science.
    On the diffusion of NV defects in diamond2012In: Physica Status Solidi (a) applications and materials science, ISSN 1862-6300, E-ISSN 1862-6319, Vol. 209, no 9, p. 1765-1768Article in journal (Refereed)
    Abstract [en]

    Besides their importance for quantum information processing, NV defects are crucial agents for the diffusion and aggregation of nitrogen in diamond. In the absence of transition metals, it is thought that the first stage of nitrogen aggregation, where close neighbour nitrogen pairs are formed, is mediated by NV defects. Here we use density functional theory to explore the barriers to NV diffusion. We conclude that the barrier is around 5 eV when there is a ready source of vacancies and that this barrier is weakly dependent on pressure.

  • 11.
    Santos, Paulo
    et al.
    Department of Physics and I3N, University of Aveiro, Campus Santiago.
    Coutinho, José
    Department of Physics and I3N, University of Aveiro, Campus Santiago.
    Öberg, Sven
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Vaqueiro-Contreras, Michelle
    Department of Physics and I3N, University of Aveiro, Campus Santiago.
    Markevich, Vladimir P.
    Photon Science Institute, University of Manchester.
    Halsall, Matthew P.
    Photon Science Institute, University of Manchester.
    Peaker, Anthony R.
    Photon Science Institute, University of Manchester.
    Theory of a carbon-oxygen-hydrogen recombination center in n-type Si2017In: Physica Status Solidi (a) applications and materials science, ISSN 1862-6300, E-ISSN 1862-6319, Vol. 214, no 7, article id 1700309Article in journal (Refereed)
    Abstract [en]

    We have recently found that in-diffusion of hydrogen into n-type Si crystals containing oxygen and carbon impurities can result in the formation of powerful recombination centers (M. Vaqueiro-Contreras et al., to appear in PSS RRL). Here, we describe a combination of first-principles calculations and electrical measurements to investigate the composition, structure, electrical activity and recombination mechanism of a carbon-oxygen-hydrogen complex (COH) in Si. We found a defect comprising a carbon-oxygen complex connected to an H atom whose location depends on the charge state of the complex, and showing a calculated acceptor level at Ev+0.3eV, a few meV away from the observations. Bistable carbon-oxygen-hydrogen complex in silicon. Carbon, oxygen, hydrogen, and silicon atoms are shown in gray, red, black, and white, respectively

  • 12.
    Sque, S.J.
    et al.
    School of Physics, University of Exeter.
    Jones, Robert
    School of Physics, University of Exeter.
    Öberg, Sven
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mathematical Science.
    Briddon, P.R.
    School of Natural Science, University of Newcastle upon Tyne.
    Theoretical study on the adsorption of armchair carbon nanotubes on the hydrogenated surface of diamond2006In: Physica Status Solidi (a) applications and materials science, ISSN 1862-6300, E-ISSN 1862-6319, Vol. 203, no 12, p. 3107-3113Article in journal (Refereed)
    Abstract [en]

    First-principles density-functional theory has been used to investigate the interaction of (metallic) (7,7) carbon nanotubes with the hydrogenated (001) surface of diamond. There is no evidence for a significant chemical interaction between the nanotubes and the diamond surface, although an appreciable binding energy is obtained. The corresponding electronic band structures are indicative of moderate electron transfer from the diamond substrate to the nanotube, which would in practice leave behind a mobile layer of holes. These results suggest that carbon nanotubes may, like buckminsterfullerene, act as suitable p-type transfer dopants for diamond.

  • 13.
    Tiwari, Amit K.
    et al.
    School of Electrical and Electronic Engineering, Newcastle University, Newcastle upon Tyne.
    Goss, J.P.
    School of Electrical and Electronic Engineering, Newcastle University, Newcastle upon Tyne.
    Briddon, P.R.
    School of Electrical and Electronic Engineering, Newcastle University, Newcastle upon Tyne.
    Wright, N.G.
    School of Electrical and Electronic Engineering, Newcastle University, Newcastle upon Tyne.
    Horsfall, A.B.
    School of Electrical and Electronic Engineering, Newcastle University, Newcastle upon Tyne.
    Jones, R.
    School of Physics, University of Exeter.
    Pinto, H.
    School of Physics, University of Exeter.
    Rayson, Mark
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mathematical Science.
    Thermodynamic stability and electronic properties of F- and Cl-terminated diamond2012In: Physica Status Solidi (a) applications and materials science, ISSN 1862-6300, E-ISSN 1862-6319, Vol. 209, no 9, p. 1709-1714Article in journal (Refereed)
    Abstract [en]

    The chemical termination of diamond has important consequences for its electrical and chemical properties. Despite the impressive potential for various scientific and technological applications, halogen termination of diamond is not fully understood. We find using first principle atomistic simulation that 100% fluorinated diamond (100) surface exhibit a chemically stable positive electron affinity of 2.13 eV, whereas 100% chlorination is energetically unfavourable. The positive electron affinity of halogenated diamond generally increases with increasing surface coverage. For mixed halogen and hydrogen termination, a wide range of negative and positive electron affinities can be achieved theoretically by varying the relative concentrations of adsorbed species.

  • 14.
    Tiwari, Amit K.
    et al.
    School of Electrical and Electronic Engineering, Newcastle University, Newcastle upon Tyne.
    Goss, J.P.
    School of Electrical and Electronic Engineering, Newcastle University, Newcastle upon Tyne.
    Briddon, P.R.
    School of Electrical and Electronic Engineering, Newcastle University, Newcastle upon Tyne.
    Wright, N.G.
    School of Electrical and Electronic Engineering, Newcastle University, Newcastle upon Tyne.
    Horsfall, A.B.
    School of Electrical and Electronic Engineering, Newcastle University, Newcastle upon Tyne.
    Rayson, Mark
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mathematical Science.
    Bromine functionalisation of diamond: an ab initio study2012In: Physica Status Solidi (a) applications and materials science, ISSN 1862-6300, E-ISSN 1862-6319, Vol. 209, no 9, p. 1703-1708Article in journal (Refereed)
    Abstract [en]

    Immobilisation of organic molecules on diamond surfaces is of great interest for biomedical applications. While H, F and Cl terminations, as a linker, have been studied extensively, the bromination of diamond is not fully understood. We have performed ab initio simulations to investigate the chemisorption of Br onto C- and H-terminated diamond (100) surfaces. We find that due to steric interaction, 100% surface coverage of Br is not stable, however, surface coverage up to around 50% is theoretically achievable. The chemisorption energies corresponding to lower surface coverages of Br are found comparable to those of hydrogen. Partial surface coverages (25 and 50%) of Br on C-terminated diamond exhibit nearly equal positive electron affinities of 0.45 and 0.52 eV, respectively. Addition of hydrogen reduces the electron affinity and for 25% of Br on an otherwise H-terminated surface, a negative electron affinity of 0.57 eV is calculated.

  • 15.
    Tiwari, Amit K.
    et al.
    School of Electrical and Electronic Engineering, Newcastle University, Newcastle upon Tyne.
    Goss, J.P
    School of Electrical and Electronic Engineering, Newcastle University, Newcastle upon Tyne.
    Briddon, P.R.
    School of Electrical and Electronic Engineering, Newcastle University, Newcastle upon Tyne.
    Wright, N.G.
    School of Electrical and Electronic Engineering, Newcastle University, Newcastle upon Tyne.
    Horsfall, A.B.
    School of Electrical and Electronic Engineering, Newcastle University, Newcastle upon Tyne.
    Rayson, Mark
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mathematical Science.
    Effect of different surface coverages of transition metals on the electronic and structural properties of diamond2012In: Physica Status Solidi (a) applications and materials science, ISSN 1862-6300, E-ISSN 1862-6319, Vol. 209, no 9, p. 1697-1702Article in journal (Refereed)
    Abstract [en]

    The presence of adsorbate species on diamond surfaces, even in relatively small concentrations, strongly influences electrical, chemical and structural properties. Despite the technological significance, coverage of diamond by transition metals has received relatively little attention. In this paper, we present the results of density functional calculations examining up to a mono-layer of transition metals on the (001) diamond surface. We find that addition of carbide forming species, such as Ti, results in significantly higher adsorption energies at all surface coverages relative to non-carbide forming species. For monolayer coverage by Cu, and sub-monolayer coverage by Ti, we find a negative electron affinity. We propose that based upon the electron affinities and binding energies, metal-terminated (001) diamond surfaces are promising candidates for electron emission device applications.

1 - 15 of 15
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